摘要Atrial fibrillation (AF) is the most frequent arrhythmia.Due to population aging,AF is a growing epidemic and its importance will continue to increase in the next decades.[1] Although the prevalence of AF is high in advanced age,the number of subjects with predisposing factors for AF is even higher.Most of these factors increase the risk of atrial fibrosis,an important component of atrial arrhythmia mechanisms.In fact,the new techniques to detect atrial fibrosis are showing the strong association between atrial fibrosis and AF risk.Regarding predisposing factors for AF,interatrial block (IAB) seems to be a key factor.The diagnosis of IAB is easy to perform using the surface ECG.It is partial when the P wave duration is ≥ 120 ms,and advanced if furthermore the P wave presents a biphasic pattem in Ⅱ,Ⅲ and VF.